Glucokinase (GK) (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1) is one of the four types of mammalian hexokinases (hexokinase IV). Hexokinases are enzymes in the first step of the glycolysis pathway which catalyze the reaction from glucose to glucose-6-phosphate. Expression of glucokinase is largely localized in the liver and pancreatic beta cells, and it plays an important role in glucose metabolism throughout the body by controlling the rate limiting step of glucose metabolism in these cells. The glucokinase types expressed in the liver and pancreatic beta cells differ in the sequence of the 15 N-terminal amino acids due to a difference in splicing, but their enzymatic properties are identical. The enzyme activities of the three hexokinases (I, II, III) other than glucokinase become saturated at a glucose concentration of below 1 mM, whereas the Km of glucokinase for glucose is 8 mM, or close to the physiological glucose level. Thus, glucokinase-mediated intracellular glucose metabolism is accelerated in response to glucose level changes by postprandial glucose level increase (10-15 mM) from normal glucose (5 mM).
The theory that glucokinase acts as a glucose sensor for pancreatic beta cells and the liver has been advocated for about 10 years. Recent results in glucokinase gene-manipulated mice have confirmed that glucokinase does in fact play an important role in systemic glucose homeostasis. Mice lacking a functional glucokinase gene die shortly after birth, while mice overexpressing glucokinase have lower blood glucose levels. With glucose level increase, the reactions of pancreatic beta cells and the liver, while differing, both act toward lowering blood glucose. Pancreatic beta cells secrete more insulin, while the liver takes up glucose and stores it as glycogen while also reducing glucose release.
Such variation in glucokinase enzyme activity is important for liver and pancreatic beta cell-mediated glucose homeostasis in mammals. A mutant form of the glucokinase gene is expressed in a type of diabetes which occurs in youth, known as MODY2 (maturity-onset diabetes of the young), and the reduced glucokinase activity has been shown to be responsible for blood glucose increase. On the other hand, families have been found having a mutation which increases glucokinase activity, and such individuals exhibit hypoglycemic symptoms.
This suggests that in humans as well, glucokinase functions as a glucose sensor and thus plays an important role in glucose homeostasis. Glucose regulation utilizing a glucokinase sensor system should be possible to achieve in type II diabetic patients. Since glucokinase activators should have effects of accelerating insulin secretion by pancreatic beta cells and of promoting glucose uptake and inhibiting glucose release by the liver, they are potentially useful as therapeutic agents for type II diabetic patients.
In recent years it has been demonstrated that pancreatic beta cell glucokinase is expressed locally in rat brain, and particularly in the ventromedial hypothalamus (VMH). Approximately 20% of VMH neurons are known as “glucose-responsive neurons”, and these have long been considered to play an important role in body weight control. Administration of glucose into rat brain reduces feeding consumption, but inhibiting glucose metabolism by intracerebral administration of the glucose analog glucosamine produces hyperphagia. Electrophysiological experiments have indicated that glucose-responsive neurons are activated in response to physiological glucose level changes (5-20 mM) but that their activation is inhibited with glucose metabolism inhibition by glucosamine or the like.
The glucose level-detecting system in the VMH is believed to be based on a glucokinase-mediated mechanism similar to that for insulin secretion by pancreatic beta cells. Consequently, substances which activate glucokinase in the VMH in addition to the liver and pancreatic beta cells not only exhibit a blood glucose rectifying effect but can also potentially rectify obesity, which is a problem for most type II diabetic patients.
This indicates that compounds having glucokinase-activating effects are useful as therapeutic and/or prophylactic agents for diabetes, as therapeutic and/or prophylactic agents for diabetes complications such as retinopathy, nephropathy, neuropathy, ischemic heart disease, arteriosclerosis and the like, and as therapeutic and/or prophylactic agents for obesity.
An example of a compound which is structurally similar to the present invention is the compound represented by the formula (III) disclosed by International Publication No. WO00/26202.

However, the aforesaid compound does not have an amino group in the benzamide skeleton, and is clearly different structurally from the compound of this application. Also, the compound in the aforesaid formula (III) is used as a CDK inhibitor and an anti-cancer agent, and in International Publication No. WO00/26202, there is no mention or suggestion regarding its use in diabetes mellitus.
The compound represented by the formula (IV) is disclosed by International Publication No. WO00/39118.

This compound (IV) does not have a nitrogen atom adjacent to the carbon atom bonded to the nitrogen atom of the NH group of carbamoyl, and differs structurally from the compound of this application. The aforesaid compound (V) is used in relation to Factor Xa, but it is different from the diabetes mellitus which is the usage described in this application. Also, in WO00/No. 39118 wherein the compound (IV) is disclosed, there is no mention or suggestion to the effect that it is useful as a treatment or prevention agent for diabetes mellitus.
The compound represented by the formula (V) is disclosed by International Publication No. WO00/39118.

However, this compound (V) has a piperazinyl group on the carbonyl side of the amide, and clearly differs structurally from the compound of this application. These compounds are related to Factor Xa inhibitor. Also, their usage is clearly different from diabetes mellitus which is the usage for the compound of this application, and there is no suggestion in this report that these compounds are useful in diabetes mellitus.
The compound represented by the formula (VI) is disclosed by Japanese Patent Application Laid-Open No. 64-25764.

However, this compound has a nitro group in the benzamide skeleton, and differs structurally from the compound of this application which has an amino group.
The compound represented by the formula (VII) is disclosed by WO01/No. 10865 as an example of a compound which is effective in the treatment of diabetes mellitus.

However, since the compound shown in formula (VII) has a methoxy group in R1 and does not have an amino group in the benzamide skeleton, it differs structurally from the compound of this application.